1. Field of the Invention
The present invention relates to methods of making gas generation compositions, and to the compositions made by those methods which are mixtures of solid particles containing organic material, and which may have utility as explosives or as gunpowder substitutes.
2. Description of the Prior Art
From the date of their earliest discovery in ancient China, compositions which generate large volumes of gas when they are subjected to combustion have been found to be suitable for use as fuels, as explosives, as propellants, including as propellants for ammunition, as a deflagrating agents, and as a pyrotechnic compounds. Such gas generation compositions have generally included a fuel component and an oxidizer component. In chemical terms, the fuel component serves as a reducing agent, and the oxidizer component serves as an oxidizing agent. By way of example, black powder has been used for centuries as a gas generation composition, and especially as gunpowder. Black powder is commonly composed of an intimate mixture of potassium nitrate, sulfur and charcoal. In black powder, potassium nitrate is the oxidizing agent, while the sulfur and charcoal comprise the fuel component. The end products resulting from the combustion of black powder are noxious smoke, hot residue, and materials which foul most weapons in which the material is discharged. Black powder also exhibits some hygroscopicity, which can limit its shelf life and which creates unpredictability as to its performance. In addition, black powder is easily ignited, and is therefore extremely dangerous to manufacture, to store and to handle. The deficiencies exhibited by black powder are a direct result of the fuel and oxidizer materials which comprise black powder.
Gas generating compositions have been formulated which exhibit improved safety or performance characteristics over black powder when used as a gunpowder. One such composition is Pyrodex.RTM., a composition of potassium nitrate, sulfur, charcoal, potassium perchlorate, various binders and modifiers and other constituents.
Another such gunpowder substitute is described in Kurtz U.S. Pat. No. 4,497,676. This reference describes a technique for making such a composition from an aqueous slurry of an organic acid, such as ascorbic or erythorbic acid, and an inorganic nitrate, such as potassium nitrate, which, when heated to drive off the water, produces a composite material which is useful as an explosive and propellent. The material is ballistically comparable in performance to black powder.
Kurtz U.S. Pat. No. 4,728,376 describes an improvement in the composition of the Kurtz '676 patent, wherein the mixture is heated at elevated temperatures during processing. The heating produces a clearly identifiable reaction which results in a chemical and/or physical change in the organic acid portion.
The requirement in the above-referenced patents to utilize a cooking process degrades the organic acid, and causes limited performance capabilities and excessive hygroscopicity, which, in turn, leads to product storage, handling and performance problems. Also, during the cooking process, the ignition and explosion danger increases dramatically, especially when the composition is produced in bulk.
An effort to overcome the above-identified disadvantages is taught in Wehrli U.S. Pat. No. 4,997,496. Wehrli describes an explosive and propellent composition comprising an admixture of ascorbic acid and a nitrate-containing oxidation agent which does not require the same cooking processes as the above-identified Kurtz patents. However, in order to achieve a useful level of ballistic performance of the type required, for example, in a variety of explosive and propellent applications, the Wehrli composition requires initial grinding and milling of both the ascorbic acid and the oxidation agent for from 25 to 30 hours in order to obtain a particle size of about 10 microns or less. The achievement of such small particle sizes requires such long grinding and milling times that the handling time and expense in producing the composition is dramatically increased, and the long handling time also increases the danger potential during the production of the composition.